Coulter began competing in US Squash tournaments in the spring of 2010. By February of 2012, he won his first Gold tournament. In Feb. of 2013 he came in 2nd in a JCT and 5th at Nationals and consistently placed in the top ten in these tournaments throughout the year. Over the next several years he achieved a #2 ranking in the U11, and #3 ranking in the U13 age group. Coulter played for 2 years on the Bronxville Middle School Team (the team won the National Championship in 2015) and played for one year on the Brunswick Middle School Team. The Brunswick team was undefeated and was the #1 seed for the Middle School National tournament, but the team had to withdraw due to weather issues. In 2016, Coulter won the U15 New York Regional Closed tournament and represented the US at the Battle of The Borders. In 2017 Coulter won the Baltimore JCT defeating the #1 and #3 in the country along the way. This victory catapulted his ranking inside the top 10 finishing off his U15 age group at a career heights of #8.